Multiple Sunscreen Chemicals Enter Your Blood After One Use—And Stay There for Days

Several chemicals commonly used in sunscreens can be absorbed into the bloodstream at levels surpassing safety thresholds, even after one application, according to a new study from the Food and Drug Administration (FDA). While the results will help experts evaluate safety guidelines, more research needs to be done—meaning you definitely shouldn’t stop using sunscreen.

For the study, which was published in JAMA, researchers had 48 healthy men and women apply various forms of sunscreen lotions and sprays containing six chemical ingredients—avobenzone, oxybenzone, octocrylene, homosalate, octisalate, and octinoxate—for four days.

The participants were asked to apply sunscreen on 75% of their bodies on day one of the trial. One days two through four, they were asked to use the same amount of sunscreen at four different times during the day every two hours.

After analyzing blood samples over a 21-day period, the researchers discovered that after the initial sunscreen application, the concentration of the six chemicals increased within the bloodstream each day it was applied, and stayed above FDA-mandated safety levels at day seven—which was after the study participants had stopped applying it. Not only that, levels of the ingredients homosalate and oxybenzone were still above safety thresholds on day 21.

The findings support those from a pilot study conducted by the FDA last year, which also found that four popular chemical sunscreen ingredients (avobenzone, oxybenzone, octocrylene, and ecamsule) were easily absorbed into the skin and went into the bloodstream after one day of use.

While the results “support the need for additional studies to determine the clinical significance,” the authors also stressed that “these findings do not indicate that individuals should refrain from the use of sunscreen.”

But why are certain sunscreen chemicals so controversial?

Last year, the FDA released a report that removed a majority of common sunscreen ingredients off its “Generally Recognized as Safe and Effective” (GRASE) list. Only two—zinc oxide and titanium dioxide—made the cut. That does not mean the others were classified as dangerous. The FDA just needs more data to be collected to ensure these ingredients meet safety standards.

While many of these chemicals are viewed as “potentially” harmful, there’s a lot scientists still don’t know about them, says Jamie Alan, Pharm. D, Ph.D., an assistant professor of pharmacology and toxicology at Michigan State University, pointing out that even the study’s authors say they don’t understand the significance of their findings.

“Avobenzene is thought to be relatively non-toxic on its own,” she says. But some data suggests that when avobenzene is combined with chlorine, it can be toxic. “This was from just one study, so we need more information,” Alan explains.

The problem: Scientists don’t have enough data to solidify these findings and determine what it actually means for your health, Alan says.

Got it, so why should I keep using sunscreen?

The FDA’s most recent findings don’t prove that the chemicals cause harm once they enter your blood. “The fact that an ingredient is absorbed through the skin and into the body does not mean that the ingredient is unsafe, nor does the FDA seeking further information indicate such,” Janet Woodcock, M.D., director of the FDA’s Center for Drug Evaluation and Research, said in a statement. “Rather, this finding calls for further industry testing to determine the safety and effect of systemic exposure of sunscreen ingredients, especially with chronic use.”

What if I prefer to avoid these chemicals anyway? Are there safer options?

Again, the FDA considers zinc oxide and titanium dioxide safe to use. “We have the most data on these compounds,” Alan says.

However, these ingredients are mineral filters (meaning they reflect UV rays), so they don’t always look transparent like chemical filters (which absorb UV rays and release them from the skin). “They are really thick and pasty,” Alan says.